A report compiled for government advisory body the Broadband Stakeholder Group (BSG) has warned that gaps in broadband speeds between metropolitan and rural areas will continue unless some "lateral thinking" is deployed.

BSG chief executive Antony Walker warned that "if rural areas are to be served in a reasonable time-frame, thinking needs to start now about creative solutions for making them more attractive to investment".

The Analysys Mason report puts the cost of a nationwide optical fibre rollout somewhere between £5.1bn and £28.8bn, depending on the technology used, and warned that connecting rural areas "will far exceed the costs in urban areas".

Analysys Mason partner Matt Yardley, who directed the work, said: "The magnitude of the costs, and how the costs differ between urban and rural areas, will be important for operators, media players and public sector organisations looking to develop their future broadband strategies."

Under the Analysys Mason model, the national deployment of fibre-to-the-cabinet, the cheapest option, would cost £5.1bn, a figure three to four times that spent by carriers on the current broadband infrastructure.

The more expensive option of fibre-to-the-home would cost £28.8bn, the biggest cost component being the civil infrastructure required to install fibre in new or existing ducts.

Analysys Mason said that these costs could be reduced significantly by the " reuse of existing telecoms ducts, the sharing of alternative infrastructure owned by other utilities such as water companies, and the use of overhead fibre distribution in some areas".

The report adds spice to a government review of next-generation broadband access in the UK, due to be presented to ministers, including Alastair Darling, later this autumn.

Heading up the review for the Department of Business, Enterprise and Regulatory Reform, is Francesco Ciao, vice chairman of Lehman Brothers Europe and chairman of the European Advisory Board, an independent committee created to advise the EC on design and implementation of EU research policy.